In my state electricity costs about $0.089/kWh. We spend about $100/mo on electricity total which comes out almost exactly to your 30kWh/day figure (with a $23.15 connection charge included).

Invested that 40k would conservatively cover over 2x our electricity bill without touching the principal (inflation adjusted).

That's a pretty hard sell for solar. Obviously incentives will improve things but it just seems less financially risky to use grid power.